Agrotis robusta (Blanchard, 1852) (Lepidoptera: Noctuidae) is a species of economic importance in South America. This species is considered a pest on seedlings of several crops. Agrotis robusta is commonly confused with and treated as A. malefida Guenée in Boisduval and Guenée, 1852, and only a couple of works cite A. robusta for South America and none mention it as a species of economic importance. The aim of this work is to redescribe and illustrate the adult and male and female genitalia of A. robusta, and to provide an identification key to closely related pest species in South America with which A. robusta has been confused. Four new synonymies with A. robusta are established: A. aureolum Schaus, 1898, Scotia koehleri Berio, 1963, S. (Feltia) fulvaurea Köhler, 1966, and S. (F.) ancastiensis Köhler, 1966.

Agrotis Ochsenheimer (Lepidoptera: Noctuidae) is a diverse (300 species) genus with a worldwide distribution, occurring in all continents except the poles. The genus belongs to the "cutworm" group (Lafontaine, 2004), Agrotis larvae cut shoots of seedlings causing, in most cases the death of the plant. Several species are considered pests for several crops (corn, tomato, potato, etc.) (Angulo and Quezada, 1975; Igarzabal et al., 1994; Pastrana, 2004). Agrotis malefida Guenee in Boisduval and Guenee, 1852 is distributed throughout the American continent excepting the Poles, and it is commonly cited as a pest species in agricultural-oriented publications. A detailed study of the literature and specimens from different museums showed that specimens identified as A. malefida in Argentina, Chile, Paraguay, and Bolivia, in most cases, actually correspond to A. robusta (Blanchard, 1852). In museum collections, specimens of both species are usually mixed and identified as A. malefida, and same collections rarely have specimens identified as A. robusta. Moreover, A. robusta has been cited only a couple of times since its original description. Misidentification of these species makes it uncertain to establish which one or if both is the economically important species.

The aim of this work is to make a detailed redescription of A. robusta, with diagnostic characters, photos, a distributional map, and a key to differentiate this species from the closest pest species in South America.

Materials and methods

Dissections of genitalia were conducted as in Lafontaine (2004). The stain used in the dissections was Chlorazol Black E for female genitalia and male aedeagus. Genitalic morphological terminology and nomenclature of types of antennae follow Lafontaine (2004). The size of the longer antennal segment was calculated measuring its width including the branches and dividing it by the width of the central shaft.

Scotia fulvaurea form extrema Köhler, 1966: 100. Unavailable. According to the 15.2 ICZN article: "A new name published after 1960 expressly as the name of a "variety" or "form" is deemed to be infrasubspecific and as such is not regulated by the Code [Art. 1.1.1] and is excluded from its provisions [Arts. 1.3.4, 45.6.3]".

Agrotis koehleri: Dapoto et al., 2003: 70. Diagnosis. Agrotis robusta can be differentiated from other South American Agrotis species by the following combination of characters: 1) patagia and tegula darker than thorax; 2) subterminal line basally projected between M1-M2-M3 veins like 2 basally black and light brownish ended arrows, and 3) male genitalia vesica without basal spined band.

Distribution. From Paraguay and Bolivia to southern Chile and Argentina (Fig. 2). In Argentina, it occurs in almost every province, from Salta to Santa Cruz. It is likely that it extends to southern Brazil and Uruguay, but we could not see specimens from these countries. Biology. There are several publications dealing with the biology of this species. Angulo and Weigert (1975a) redescribed and provided a key to immature stages. Angulo and Quezada (1975) and Igarzábal et al. (1994) gave a detailed description of the immature stages, adults, and species life cycle. In these works, A. robusta is treated as Feltia malefida.

Over the years researchers have confused A. robusta with A. ipsilon and A. malefida. In southern South America, specifically Argentina, Chile, Paraguay, and Bolivia, A. malefida is considered a pest of several crops, but in fact most of those specimens correspond to A. robusta. Agrotis malefida extends throughout the American continent except the Poles, but it is relatively rare in southern South America, supported on the number of specimens in collections. Even though we know that pest species are not always well represented in museum collections and this could be a sample bias, we think that evidence from different works, especially agricultural ones, supports this affirmation. Based on current evidence we think that A. malefida it is not a pest species in this region as could be A. robusta.

Agrotis robusta, A. malefida, and A. ipsilon (Hufnagel, 1766) are relatively large moths (forewing length between 16 and 20 mm) and can be identified with the following key:

To the following curators for loans of material: Michael Pogue and Patricia Gentili (USNM), Virginia Colomo (IMLA), and Don Lafontaine (CNC). Special thanks to Jerome Barbut (MNHN) for the photos of the type of Noctua robusta Blanchard and to Ulf Buchsbaum for looking up for Kohler's type specimens at the collection of the Zoologische Staatssammlung, Munich, Germany. To Michael Pogue, Don Lafontaine, and Federico Ocampo for valuable suggestions and advice. Also we want to thank 2 anonymous reviewers for important recommendations that helped improve the mansucript. The Instituto de Investigaciones de las Zonas Áridas provided workspace and equipment. This study was supported by the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET).